Sikkim in north-eastern India; Mammal Diversity Database also lists Bhutan and China
The Sikkim pika, or Sijin pika, is a pika known from the state of Sikkim in north-eastern India. Its separation as a species was supported by later analyses of mitochondrial DNA. It is closely related to the Nubra pika (Wikipedia, general species account).
The only source opened is a short account that gives no description, size, habitat or diet. The Mammal Diversity Database lists India, Bhutan and China for the species, so a Bhutan record is plausible but not detailed here. The entry is kept short on purpose.
Description: Wildlife of Bhutan guide, Wildlife of Everywhere (wildlifeofeverywhere.com); general species information paraphrased from Wikipedia (CC BY-SA)
Mammals of the World